The idea, as I understand it, is that the person who has paid for the service would be able to form LFD groups out of their own realID friend list (you already have the ability to chat to them while playing).

Basically, you could reap the benefits of LFG without ‘having’ to group with the great unwashed.

Since people who actually form their own groups are likely to be the more social players anyway, Blizzard effectively will be going the opposite way from Valve and charging the people who most want and are able to build social networks for their friends. I am sure people will pay for this. But clearly it is cheaper to just be friends with someone who pays for the service and hang on their coat tails, assuming you like the groups they form.